Methods for fabricating optical metasurfaces

Abstract

Methods of fabricating optical metasurfaces are provided which may comprise forming a free-standing membrane from a wafer and forming a metasurface pattern in the free-standing membrane to provide an optical metasurface comprising the free-standing membrane having defined therein, a periodic array of flow-through apertures, the flow-through apertures having subwavelength dimensions and arranged according to the metasurface pattern, wherein the metasurface pattern is configured to confine incoming light within the flow-through apertures. The optical metasurfaces and devices (e.g., sensors and spectrometers) comprising the optical metasurfaces are also provided.

1 . A method of fabricating an optical metasurface, the method comprising forming a free-standing membrane from a wafer and forming a metasurface pattern in the free-standing membrane to provide an optical metasurface comprising the free-standing membrane having defined therein, a periodic array of flow-through apertures, the flow-through apertures having subwavelength dimensions and arranged according to the metasurface pattern, wherein the metasurface pattern is configured to confine incoming light within the flow-through apertures. 
     
     
         2 . The method of  claim 1 , wherein the metasurface pattern is configured to support an optical mode characterized by an enhanced electric (E) field within the flow-through apertures. 
     
     
         3 . The method of  claim 2 , wherein the enhanced E field of the optical mode throughout the flow-through apertures is greater than an enhanced E field of a photonic crystal guided mode throughout the flow-through apertures. 
     
     
         4 . The method of  claim 2 , wherein the optical mode is a bound state in the continuum (BIC) optical mode. 
     
     
         5 . The method of  claim 4 , wherein the BIC optical mode is a BIC TE optical mode. 
     
     
         6 . The method of  claim 2 , wherein the enhanced E field is capable of inducing vibrational strong coupling between a molecule present in the flow-through apertures and the optical mode and generating a polariton pair. 
     
     
         7 . The method of  claim 2 , wherein the enhanced E field is at least 50 throughout the flow-through apertures. 
     
     
         8 . The method of  claim 1 , wherein the incoming light is mid-infrared light. 
     
     
         9 . The method of  claim 1 , wherein the free-standing membrane is composed of a dielectric material selected from Group IV elements or Group III-V semiconductors. 
     
     
         10 . The method of  claim 1 , wherein the free-standing membrane is free of a conductive material. 
     
     
         11 . The method of  claim 1 , further comprising forming a resist layer having a resist pattern therein, the resist pattern corresponding to the metasurface pattern. 
     
     
         12 . The method of  claim 11 , further comprising applying the resist layer to a surface of the free-standing membrane prior to forming the resist pattern therein. 
     
     
         13 . The method of  claim 1 , wherein forming the free-standing membrane comprises patterning an opening into a handle of the wafer and etching to release the free-standing membrane; and
 further wherein forming the metasurface pattern comprises applying a resist layer on a surface of the free-standing membrane, forming a resist pattern in the resist layer, the resist pattern corresponding to the metasurface pattern, and etching the free-standing membrane to provide the flow-through apertures.   
     
     
         14 . The method of  claim 1 , wherein the free-standing membrane has a thickness of no greater than 10 μm and the subwavelength dimensions are each no greater than 10 μm. 
     
     
         15 . The method of  claim 1 , wherein the metasurface pattern comprises a repeating metaunit comprising four apertures each having a radius r 1  and arranged in a square array; and a central aperture having a radius r 2  wherein r 1 >r 2 . 
     
     
         16 . The method of  claim 1 , wherein the metasurface pattern comprises a repeating metaunit comprising two elliptical apertures tilted away from one another. 
     
     
         17 . An optical metasurface comprising a free-standing membrane having defined therein, a periodic array of flow-through apertures, the flow-through apertures having subwavelength dimensions and arranged according to a metasurface pattern, wherein the metasurface pattern is configured to confine incoming light within the flow-through apertures. 
     
     
         18 . A sensor comprising the optical metasurface of  claim 17 , a sample delivery assembly configured to deliver a sample to at least one of the flow-through apertures; a light source configured to provide the incoming light; and a detector configured to detect light transmitted through the optical metasurface. 
     
     
         19 . The sensor of  claim 18 , wherein the sample delivery assembly is a component of, or is in fluid communication with, a microfluidic control system. 
     
     
         20 . A spectrometer comprising an array of optical metasurfaces according to  claim 17 , wherein each metasurface pattern of each optical metasurface has a different resonance wavelength λ res  and resonance bandwidth; a light source configured to provide the incoming light; and a detector configured to detect light transmitted through the array of optical metasurfaces.